Electronic signals are used to communicate information between different nodes in a network. When generating a signal, it is often desirable that the signal has certain characteristics. For instance, suppose the signal is to be transmitted over a conductive medium. That conductive medium serves the desirable function of a conduit through which the signal may travel. Often, however, as the signal passes through the conductive medium, the conductive medium may take on the secondary and often undesirable function of an antenna. In other words, the signal may cause Electro-Magnetic Interference (EMI) to be emitted into the ambient environment.
The ambient environment may be sensitive to EMI emissions, depending on the frequency of the EMI emissions. For instance, EMI emissions at some frequencies may adversely affect surrounding circuitry. EMI emissions at some frequencies at excessive levels may be a violation of the law, since there are often strict controls over certain bands of airwave transmissions.
The EMI emitted into the ambient environment typically has some of the same frequency components as the signal that travels over the conductive medium. Accordingly, by controlling the frequency characteristics of the signal passing through a conductive medium, one can also control the frequency characteristics of the unintended EMI emissions emitted into the ambient environment.
One mechanism to control the frequency characteristics of the EMI emissions caused by a signal is to control the speed at which a signal transitions from one level to another. This is often termed “slope control”. For instance, in a binary signal, as the signal transitions from high to low, and low to high, the speed at which the transition occurs is moderated. This has the effect of attenuating some of the higher frequency components of the EMI emissions.